Wireless communication systems generally comprise a set of radios and a set of base sites. The radios, which may be mobile radios, portable radios or the like, are generally the endpoints of a communication path, while base sites are typically stationary intermediates by which a communication path to a radio device is established or maintained.
During operation of a communication system, there are instances where it is desirable to provide voice communication to multiple users in the communication system. For example, in transit systems (e.g., communication systems for public transportation vehicles), radios typically operate in a data only mode. If a dispatcher desires to establish a voice call to many or all of the vehicles (also referred to as a Public Announcement Call), the dispatcher can initiate transmission of a broadcast data message to the vehicles that are to receive the public announcement. Upon receiving this broadcast data message, application software coupled to the radio interprets the message and instructs the radio to affiliate to a public announcement channel. The radio then attempts to do so by transmitting an affiliation request to the base site.
Such systems, however, has several drawbacks. For example, in systems with large numbers of radios, affiliation requests sent immediately from multiple radios may collide and interfere with one another. Even if the radios are configured to retry, such collisions may continue to happen, thus preventing many radios from being able to properly affiliate to the public announcement talkgroup. Additionally, even if all of the radios can be affiliated, it takes a significant amount of time to process affiliation requests from all radios in the communication system and to provide affiliation grants back to each such radio. As such, the communications system must incorporate a significant delay between the broadcast data message announcing the public announcement call and the initiation of the call to provide sufficient time to handle all the affiliation requests and grants.
Skilled artisans will appreciate that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions and/or relative positioning of some of the elements in the figures may be exaggerated relative to other elements to help improve the understanding of various embodiments of the present disclosure. Also, common but well-understood elements that are useful or necessary in a commercially feasible embodiment are not often depicted in order to facilitate a less obstructed view of these various embodiments of the present disclosure. It will be further appreciated that certain actions and/or steps may be described or depicted in a particular order of occurrence while those skilled in the art will understand that such specificity with respect to sequence is not actually required. It will also be understood that the terms and expressions with respect to their corresponding respective areas of inquiry and study except where specific meaning have otherwise been set forth herein.